This invention is related to a general purpose incandescent lamp, and more particularly, to a higher efficiency general purpose incandescent lamp comprising an outer bulb filled with an inert gas or evacuated and an inner envelope containing a halogen atmosphere along with a relatively high pressure fill-gas and a spatially disposed low voltage filament.
The continuing pursuit of improving the efficiency of lamps is of increasing importance due to the increasing cost of energy. One of the family of lamps in which the efficiency is desired to be improved is the incandescent lamp. Incandescent lamps, although having efficiency ratings lower than those of fluorescent and high intensity discharge lamps, have many attractive features, such as, low cost, compact size, instant light, dimmability, convenience, pleasing spectral distribution, and millions of existing sockets in the homes of users who have become accustomed to the pleasing incandescent type lighting.
Incandescent lamps are of various types, the most well-known is the A-line type which is typically termed a general service incandescent lamp and has a wide range of wattage ratings. Still further, the general purpose incandescent lamp typically has a tungsten type filament.
The tungsten filament is also commonly utilized in relatively more expensive but more efficient special purpose halogen type lamps. In typical operation over an extended period of time, some tungsten of the tungsten type filament evaporates and becomes deposited on the bulb wall, which, in turn, typically causes a blackening of the bulb wall, which, in turn, decreases the lumen output thereby decreasing the lumens per watt or efficacy of the lamp. It is known that the blackening of the bulb wall caused by the tungsten type filament may be substantially reduced by providing a halogen type gas atmosphere surrounding the tungsten type filament which provides a regenerative (transport) cycle that keeps the bulb wall clean resulting in improved lumen output. It is considered desirable that means for improving the efficacy, such as, a halogen type atmosphere employed in a relatively expensive special purpose halogen type lamp be adapted to a general service incandescent lamp while maintaining certain of the attractive features of the relatively inexpensive general purpose incandescent lamp.
The operation of a tungsten filament may be further improved relative to the efficacy of the incandescent lamp by housing the filament in a suitable efficient fill-gas, such as xenon, krypton or argon, raised to a relatively high pressure. The high pressure fill-gas improves the operation of the filament by reducing the evaporation of the tungsten material from the filament and also allows raising of the filament operating temperature, both contributing to improving the efficacy of the lamp. The arc-out resistance of the filament, that is, the resistance of the filament to being burned out by an arc condition within its housing, may be improved by the addition of some nitrogen gas. It is considered desirable to provide an incandescent lamp utilizing the efficacy gain realized by the high pressure fill gas of the xenon, krypton or argon, and to improve the arc-out resistance of the filament by the addition of the nitrogen gas.
Further improvements to the incandescent lamp are also desired. For example, it is desired that the life of the incandescent lamp be extended while still maintaining the efficacy of the lamp. As previously mentioned, the increase of fill-gas pressure and the use of xenon or krypton improves the operation of the filament which correspondingly increases the life of the incandescent lamp and also increases the efficacy of the incandescent lamp.
Another means for extending the life of an incandescent lamp is to reduce the operating voltage of the filament, but it is desired that this reduction of operating voltage be accomplished while maintaining the wattage and efficacy of the lamp. It is considered desirable to provide a filament that provides extended life and maintains the wattage of the lamp and even increases the efficacy of the incandescent lamp while operated at a low voltage.
It is considered desirable to provide a plurality of means which all extend the life of the incandescent lamp and which all maintain and even increase the efficacy of the incandescent lamp.
Accordingly, objects of the present invention are to provide a relatively inexpensive general service incandescent lamp having, (1) an efficient fill gas such as xenon, krypton, or argon all of a relatively high pressure and both the efficient fill-gas and the relatively high pressure contributing to improving the operation of the filament, (2) a relatively high pressure fill-gas having an addition of nitrogen so as to improve the arc-out resistance of the filament, (3) a filament operated at a low voltage so as to extend the life of the incandescent lamp while still maintaining the wattage of the lamp and even increasing the efficacy of the lamp, (4) a halogen gas atmosphere to provide a transport cycle for the evaporated tungsten, and (5) combining the relatively high pressure fill-gas having the nitrogen additive, the low voltage filament and the halogen atmosphere in such a manner that the overall effect extends the life of the incandescent lamp and provides an improved efficacy both greater than the expected gains usually realized from the individual contributors.
These and other objects of the present invention will become apparent upon consideration of the following description taken in conjunction with the accompanying drawings.